1. Field of the Invention
The present invention relates generally to the field of dental implantogy and, more specifically, to apparatus for safely and effectively installing the implant in a prepared surgical site without damaging the implant.
2. Background Information
Dental implants play an extraordinarily important role in modem dentistry. Implants serve as the foundation for a variety of dental prostheses as may be provided to correct debilitating or embarrassing conditions caused by, for example, disease, accident or natural aging.
In order to adequately support the dental prosthesis for which it is intended, the implant (also referred to as a “fixture”) is surgically implanted into healthy bone tissue of the patient's alveolar (jaw) bone. To install the implant, the surgical site is prepared by first incising the gingival tissue at the implant site and then drilling a generally cylindrical bore into the bone mass. The prepared bore is referred as an osteotomy. Although implants may be made in a variety of forms, a conventional and a very common implant has a generally cylindrical body that is externally threaded and tapered at one end. The taper may extend for only the distance of the first few threads or extend for nearly the entire length of the implant. In recent years, it has become conventional to apply certain coatings to the outer surfaces of the implants. These coatings, such as hydroxyapatite (HA) or Titanium Plasma Spray (TPS), enable the bone tissue to better integrate with the implant, thereby providing enhanced support for the prosthesis.
Once the osteotomy is prepared, the tapered end of the implant is positioned in the osteotomy, and a powered or manual driving tool is employed by the surgeon to rotate the implant and drive it into the osteotomy, which may or may not have been pre-threaded or tapped to receive the implant. The driving tool includes an end portion that is configured to matingly engage the end of the implant so as to transmit torque to the implant.
In some instances, both to deliver the implant to the surgical site and to drive the implant into the osteotomy, a piece referred to as a “fixture mount” is attached to the top of the implant by a retaining screw and it, rather than the implant, directly engages the driving tool. In this manner, the fixture mount serves as an intermediate member for transmitting to the implant the torque applied by the driving tool. Conventional fixture mounts have been made of metal, such as titanium.
The size of the osteotomy and the density of the bone mass at the surgical site will dictate the amount of torque that must be applied to the implant during installation. For example, where the bone density is greater than anticipated, the dental surgeon may find that an unusually high torque is required in order to implant the device. Presently, if the surgeon believes, based on tactile feedback, that the implant is experiencing excessive resistive force, such that a potentially damaging torque would have to be applied in order to install the implant, the surgeon must extract the then partially-installed implant. Typically, this is accomplished by reversing the drive tool's direction of rotation, and using the drive tool and fixture mount to “back-out” the implant from the osteotomy, which can then be widened with a larger drill or tapped as necessary.
If this procedure is not followed and, instead, an excessive torque is applied to the implant, the implant may become damaged. Such damage may take various forms. For example, the coating that is applied to the surface of the implant and that is important for enhancing bone growth may be scrapped off the implant or otherwise damaged. Furthermore, with increasing torque, the end of the implant that receives the applied torque may become damaged, much the way the head of a screw or bolt becomes stripped or rounded off. Finally, it is possible that the implant would fracture with excessive torque applied. In each instance, such damage typically would necessitate removal of the damaged implant, thereby lengthening the time required for the surgical procedure and, potentially, increasing the discomfort to the patient.
Further, with excessive torque applied to the top or driven end of the implant via the drive tool and fixture mount, the damage to the end of the implant may be such that it becomes impossible to simply back the implant out of the osteotomy using the drive tool and the fixture mount. This can further complicate the surgical procedure. Given that the implant cannot simply be backed out by rotating it in the opposite direction via the drive tool and fixture mount, other special tools and procedures need to be employed.
Once the implant is successfully installed, the still-attached fixture mount is in position to serve other functions. For example, by extending above the gum line as it does, the fixture mount may be employed to shape or direct the growth of gingival tissue during healing. Likewise, the fixture mount may be used as an impression post so that the dental surgeon or clinician may take precise impressions that are then used by a dental laboratory to manufacture a properly fitting prosthesis. Furthermore, the attached fixture mount may serve as a temporary abutment for supporting a provisional or temporary prosthesis that may be installed at the time of the original surgery and remain in place until the permanent prosthesis has been manufactured in a dental laboratory.
For use in any of these applications, however, the fixture mount may require certain modifications, particularly when used to support a temporary prosthesis. Such modifications may involve, for example, cutting, grinding or otherwise shaping the body of the fixture mount. Given that fixture mounts have been made typically of titanium or similar such metals, it has been common practice for the dental surgeon to purchase a separate component for use as the temporary abutment, one that is easier to prepare “chair-side” or that can be sent to a dental laboratory for the custom shaping that is necessary. In such instances, the fixture mount itself is discarded and the patient may be deprived of the opportunity of having a temporary prosthesis fitted at the end of the initial surgical procedure and must instead suffer the inconvenience of returning for a second procedure at a time when the temporary abutment and prosthesis can be installed. Still a third procedure is then required after the permanent prosthesis has been fabricated and is ready for installation.
Although it would be desirable for the dental surgeon himself to modify the fixture mount “chair-side,” rather than sending the piece offsite to be altered or reconfigured for use as a temporary abutment, for example, the tools available to the dental surgeon typically limit his ability to shape the fixture mount. As mentioned above, conventional fixture mounts are typically made of titanium or another very strong metal. That factor, coupled with the very small size of the fixture mount, makes it extremely difficult for the dental surgeon to make precise chair-side modifications to the fixture mount.
Accordingly, given the damage that can occur to an implant if excessive torque is applied during implantation, it would therefore be advantageous to employ an implant drive system that would limit the torque or rotational force that can be applied to the implant. Preferably, the system would incorporate and could be employed with the driving tools and implants that are presently on the market and in the current inventories of dental surgeons. Preferably, the system would limit the rotational force or torque applied to the implant to a value below that which could damage the implant and, at the same time, provide a means to withdraw the implant from the osteotomy using the same system components, rather than by having to employ additional tools or a cumbersome or more complicated procedure. Further, it would be advantageous if a drive system included a fixture mount that could be readily revised or fashioned chair-side by the dental surgeon, such that a temporary or provisional prosthesis could be fitted and installed during the same surgical procedure in which the implant is first installed.